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Discussion Starter · #1 ·
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does watt vs. amount of light produced (lumens?) work linearly, i.e do two 10W HID light bulbs produce exactly twice as much as a 10 watt and would the two 10W HID's mounted side by side produce 10% more light than an 18W HID single bulb? How would the two mixed 10W beams compare with the single 18W beam in terms of overall beam width, distance, etc etc?

hope this is making sense..
 

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<font color='#728FCE'>Could you rephrase the question...possibly into English??
 

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The brains & beauty behind 'Kinky Divers'
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<font color='#8D38C9'>phew....... not just me then!
 

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Discussion Starter · #5 ·
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erhhmmm, ok here goes:

if you take one 20W light with a given beam width and compare that with two 10W lights held side by side each with the same beamwidth, how would the two setups compare:

would the two 10W lights produce a bit less light than he 20W one because their two beams crossover?

would the two 10W produce exactly the same amount of light as the 20W

etc

howzat?
 

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<font color='#728FCE'>Now I understand the question:(
Havn't got a clue what the answer is:(
 

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<font color='#8D38C9'>

think I'll go sit in a corner & wibble, this is outside my sphere of experience.......
a boy experiment methinks!
 

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Discussion Starter · #8 ·
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wot wot, nobody on the forum with light interferometry experience! I've done some math and my own theory is that the beam from two adjacent 10W will be wider than from a single 20W. the amount of light where the two 10W beams cross could be equal to that from the 20W light (depending on number of wavelengths etc), but where the two 10W beams do not combine, you will get half the light than from a 20W bulb.

So described in english, instead of having one uniform 20W spot, you would get a smaller 20W spot, surrounded by a wider 10W "halo".
 

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<font color='#728FCE'>yes, or no, i think wibble wibble doo da sputnik!
 

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<font color='#0000FF'>
[b said:
Quote[/b] ]wot wot, nobody on the forum with light interferometry experience! I've done some math and my own theory is that the beam from two adjacent 10W will be wider than from a single 20W. the amount of light where the two 10W beams cross could be equal to that from the 20W light (depending on number of wavelengths etc), but where the two 10W beams do not combine, you will get half the light than from a 20W bulb.

So described in english, instead of having one uniform 20W spot, you would get a smaller 20W spot, surrounded by a wider 10W "halo".
Complete rubbish, well presented though!
 

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Frogkick! Don't give up. I think that's a perfectly valid question, although perhaps you are misunderstood by your public
...
I would have thought that there must be some sort of efficiency loss in having 2 bulbs rather than one, no? I mean in the sense of the interference that is going to be experienced between the bulb and the object being illuminated. And anyway there must be some issue relating to additional mass in your rig, etc. etc. So, 2 lights bad one light good?
 

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Discussion Starter · #13 ·
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one light may be better from an efficiency viewpoint, but two lights are better from a redundancy viewpoint and funnily enough two 10s cost less than one 20 (or 18W to be precise) and I already have one 10.

Also the thing that got me thinking were a couple of pics on a divernet article with a rebreather diver carrying two 10W HIDs held together. I suspect may have been a pic of Ms Trewavas?
 

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The wattage of a bulb is the amount of electrical power it consumes. This power is converted into heat and light. Normal bulbs are very inefficient and convert most of the power to heat.
HID are far more efficient and this is why for a given wattage they produce far more light.

Using two bulbs would double the power and double the light output. Dont assume though that a 15W bulb will produce 50% more light than a 10W as this depends on how the bulb is designed. You can get a whiter brighter light by making the filament in the bulb burn hotter but this reduces the life of the bulb. The bulb life can be increased by using Xeon gas inside.
 

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The short answer (having dived with people who've done it) is that the 18w would provide a better penetrating beam.

It depends why you're doing it though, some people use the twin 10's since they then also rig them as video lights, or because they like the redundancy profile it gives them.

It kinda comes down to a question of why you're doing it.....dontcha love kit  



/Zak

PS. Dont forget that the whole wattage/lumens debate also needs to take into account colour temperature.
 

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[b said:
Quote[/b] (zaksherlock @ Mar. 14 2004,11:49)]PS. Dont forget that the whole wattage/lumens debate also needs to take into account colour temperature.
<font color='#000080'>Why do you need to take colour temperature into account with the wattage / lumens debate.

This will probably have been dealt with long ago at the pounds / pence debate.

John.
 

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The debate is basically discussing which is best, 20W or 2*10W.

A standard 20W bulb due to the filament being hotter to produce the extra light will also produce a whiter light. This is where colour temperature comes into it as it defines the colour of the light.
 

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<font color='#000080'>
A standard 20W bulb due to the filament being hotter to produce the extra light will also produce a whiter light. This is where colour temperature comes into it as it defines the colour of the light.

Hi mate thats not strictly true.A 10w filament and a 20w filament of the same type will have the same colour temperature but the 20w will have more intensity.

IMO the two 10w lights would give roughly the same light output up to a certain distance where the 10w would fade off whereas the 20w would as said before still be illuminating for a greater distance.
The benefit of the two 10w apart from redundancy they would give a wider beam of light if set up properly. They would also give you a chance if need be to loose any dead spots that you sometimes get with these types of lamps, by overlapping the beams. There are a few variants to take into account with the original question distance being one of them.
Most filament bulbs will give you a colour temp of around 3200 degrees kelvin with the generally more powerful and more expencive ( my point previously) HID type bulbs are usually around 5500 degrees kelvin. You can correct the colour temperature either way by using filters but it will drop your light output.
John.
 

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Discussion Starter · #19 ·
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Been reading the answers with great interest. Zak, the purpose is to have a redundant light which gets used for every single dive alongside the primary one, vs. a redundant scout light on the harness which never gets used and could hardly compensate for the main light dying on me.

I've also figured out that combining two 10w lights if properly done (would have to figure out how to attach both heads to the same goodmans handle) would produce a wider illuminated area with a centre as bright as a 20W, but with a wider halo of 10W intensity if you see watt (..) I mean.

Also, as I've already mentioned, it's cheaper to do 2x10 than 1x18, in addition to the redundancy provided.
 

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<font color='#000080'>
(would have to figure out how to attach both heads to the same goodmans handle)

I'm curious now, what lights are you thinking of using?
John.
 
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